Here are a few thoughts on folding brochures or any other printed products. Paper always has a grain direction. Folding with the grain direction will give you a cleaner fold with less cracking. We all have seen brochures that are cracking on the folds. How do you reduce cracking? Folding with the grain will help.
Also, if you are dealing with heavy paper(let's say over 100# book) you need to score or crease the paper with a machine to help train the fold to prevent or minimize cracking. Our rule of thumb is a brochure on 80# book may or may not need to score. Anything heavier than 80# book or any weight of cover will need to be scored. Scoring will minimize cracking but will not always eliminate it on the printed product. Cracking on printed products is most noticeable when there is ink over the folds. Especially darker inks.
Scoring can be done on a letterpress or on the actual folder or other machines that crease the paper. Letterpress scoring is the best quality score you can do. On cross grain folding, I would highly recommend scoring of some method to reduce or elimininate cracking.
